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Use the site. That is the whole agreement.
You may right-click. You may view source, and honestly you should, because every image here is drawn by a few hundred lines of canvas code and there is not a single photograph in the whole thing.
You may borrow the ideas. Please do not copy the pages wholesale and put your own name on them.
The software linked from here is provided as is, which in plain language means it works on my machine and I would be glad if it works on yours.
If the office game causes you to reconsider your career, that is between you and your employer.